This work investigated the possibility of coupling the high conductivity of cerates and the good chemical stability of zirconates as proton conductor electrolytes for solid oxide fuel cells (SOFCs). Two different approaches are discussed: the synthesis of barium cerate and zirconate solid solutions, and the fabrication of a bilayer electrolyte made of a Y-doped barium cerate pellet covered by a thin protecting layer of Y-doped barium zirconate. The chemical stability of the tailored samples was tested exposing them to 100% CO2 atmosphere at 700°C for 3 h. X-ray diffraction (XRD) analysis was used to investigate the phase composition of the specimens before and after the CO2 treatment. Electrochemical impedance spectroscopy (EIS) measurements were carried out in humidified H2. Hydrogen-air breathing fuel cell experiments were carried out at 700°C.